The invention relates generally to optical waveguides.
Modern high-speed communications systems are increasingly using optical waveguides including fibers for transmitting and receiving high-bandwidth data. The excellent properties of optical waveguides with respect to flexibility and ease of handling and installation are an important driving force for their implementation in high bandwidth, short-haul data transmission applications such as fiber to the home, local area networks, high-speed computing, and automotive information, diagnostic, and entertainment systems.
In any type of optical communication system there is the need for interconnecting different discrete components. These components may include active devices, such as lasers, detectors, fibers modulators, and switches, for example, and passive devices such as filters and splitters, for example. Polymer-based waveguides offer a viable and potentially inexpensive way of interconnecting these components. Such waveguides should be able to couple light into or out with good efficiency and deliver optical signals with very low propagation losses, which in turn are determined primarily by the quality of the polymer, the waveguide structure, and the device boundary.
A proper selection of polymeric materials is necessary for making polymeric optical waveguides that display low attenuation and improved environmental stability without an excessive increase in scattering loss. Moreover, a well-defined introduction of light-confining or light-scattering elements is potentially useful to obtain controlled propagation of light in polymeric optical waveguides.
Waveguide structures can be formed by several techniques. For example, ridge waveguides can be formed by coating a lower clad and core layer onto a substrate, patterning the core by etching or development to form a ridge, and over-coating with an upper clad layer. As another example, embedded or channel waveguides can be formed by coating a lower clad and core material over a substrate, defining the waveguide by UV exposure and depositing an upper clad layer over it. Reactant diffusion occurs between the unexposed core and surrounding clad layers into the exposed core area changing its refractive index (hereinafter also referred to as “RI”) to form the waveguide.
Optical loss and energy leakage occur if a bending radius of an optical waveguide is too small. Techniques such as widening or tapering the waveguide in the region of the bend, forming offset structures in the region of the bend, and forming irregularly-shaped bends have been proposed to resolve the problem of losses. However, such techniques require complicated optimization and costly design processes and provide relatively limited enhancements.
It would therefore be desirable to have a new waveguide structure to reduce these losses and permit tighter bends.